W24×104 Steel Beam
A W24×104 is a wide flange steel beam 24.1 inches deep with 12.8-inch flanges, weighing 104 pounds per foot. In ASTM A992 steel (Fy = 50 ksi) it has a design bending strength of 1,084 kip-ft (LRFD) when its compression flange is braced, and a design shear strength of 362 kips.
Design a W24×104 beam Opens a 36 ft span in the free beam designer.
W24×104 dimensions
| Dimension | Value |
|---|---|
| Depth, d | 24.1 in |
| Flange width, bf | 12.8 in |
| Flange thickness, tf | 0.750 in |
| Web thickness, tw | 0.500 in |
| Distance to web toe of fillet, kdes | 1.25 in |
| Distance between flange centroids, ho | 23.35 in |
| Cross-sectional area, A | 30.6 in2 |
| Weight | 104 lb/ft |
Dimensions are AISC design values. Detailing dimensions are rounded to the nearest 1/16 in.
W24×104 section properties
| Property | Strong axis (x) | Weak axis (y) |
|---|---|---|
| Moment of inertia, I | 3100 in4 | 259 in4 |
| Elastic section modulus, S | 258 in3 | 40.7 in3 |
| Plastic section modulus, Z | 289 in3 | 62.4 in3 |
| Radius of gyration, r | 10.1 in | 2.91 in |
| Torsion and slenderness | Value |
|---|---|
| Torsional constant, J | 4.72 in4 |
| Warping constant, Cw | 35200 in6 |
| Effective radius of gyration, rts | 3.42 in |
| Flange slenderness, bf/2tf | 8.50 |
| Web slenderness, h/tw | 43.1 |
W24×104 bending and shear strength
For ASTM A992 steel (Fy = 50 ksi, E = 29,000 ksi) per AISC 360-16. Its flanges and web are compact for bending, so with its compression flange braced it reaches its full plastic moment.
| Strength | LRFD | ASD |
|---|---|---|
| Bending, compression flange braced | φMn = 1,084 kip-ft | Mn/Ω = 721 kip-ft |
| Shear | φVn = 362 kips | Vn/Ω = 241 kips |
If the compression flange isn't braced, the beam can buckle sideways before it yields. Up to Lp = 10.3 ft between braces it keeps its full strength; past Lr = 29.2 ft it buckles elastically. With uniform moment between braces (Cb = 1.0):
| Unbraced length, Lb | φMn (LRFD) | Mn/Ω (ASD) |
|---|---|---|
| Braced | 1,084 kip-ft | 721 kip-ft |
| 5 ft | 1,084 kip-ft | 721 kip-ft |
| 10 ft | 1,084 kip-ft | 721 kip-ft |
| 10.3 ft (Lp) | 1,084 kip-ft | 721 kip-ft |
| 15 ft | 982 kip-ft | 654 kip-ft |
| 20 ft | 875 kip-ft | 582 kip-ft |
| 25 ft | 767 kip-ft | 511 kip-ft |
| 29.2 ft (Lr) | 676 kip-ft | 450 kip-ft |
| 30 ft | 648 kip-ft | 431 kip-ft |
| 35 ft | 509 kip-ft | 339 kip-ft |
| 40 ft | 418 kip-ft | 278 kip-ft |
| 45 ft | 353 kip-ft | 235 kip-ft |
| 50 ft | 306 kip-ft | 203 kip-ft |
| 55 ft | 269 kip-ft | 179 kip-ft |
A beam with a uniform load between braces has Cb above 1.0 (1.14 for a simple span braced only at its ends), so these values are conservative. The beam designer works out Cb for every segment between braces.
W24×104 load table by span
The largest uniform load a simply supported W24×104 can carry, in kips per foot, with its compression flange braced along its length (by a floor or roof deck, for example). The loads include the beam's own weight of 0.104 kips per foot.
| Span | Factored load (LRFD) | Allowable load (ASD) | Load at span/360 | Load at span/240 |
|---|---|---|---|---|
| 12 ft | 60.2 | 40.1 | 77.1 | 115.6 |
| 14 ft | 44.2 | 29.4 | 48.5 | 72.8 |
| 16 ft | 33.9 | 22.5 | 32.5 | 48.8 |
| 18 ft | 26.8 | 17.8 | 22.8 | 34.3 |
| 20 ft | 21.7 | 14.4 | 16.6 | 25.0 |
| 22 ft | 17.9 | 11.9 | 12.5 | 18.8 |
| 24 ft | 15.1 | 10.0 | 9.63 | 14.5 |
| 26 ft | 12.8 | 8.53 | 7.58 | 11.4 |
| 28 ft | 11.1 | 7.36 | 6.07 | 9.10 |
| 30 ft | 9.63 | 6.41 | 4.93 | 7.40 |
| 32 ft | 8.47 | 5.63 | 4.06 | 6.10 |
| 34 ft | 7.50 | 4.99 | 3.39 | 5.08 |
| 36 ft | 6.69 | 4.45 | 2.85 | 4.28 |
| 38 ft | 6.00 | 3.99 | 2.43 | 3.64 |
| 40 ft | 5.42 | 3.61 | 2.08 | 3.12 |
| 42 ft | 4.91 | 3.27 | 1.80 | 2.70 |
| 44 ft | 4.48 | 2.98 | 1.56 | 2.35 |
| 46 ft | 4.10 | 2.73 | 1.37 | 2.05 |
| 48 ft | 3.76 | 2.50 | 1.20 | 1.81 |
| 50 ft | 3.47 | 2.31 | 1.07 | 1.60 |
| 52 ft | 3.21 | 2.13 | 0.95 | 1.42 |
| 54 ft | 2.97 | 1.98 | 0.85 | 1.27 |
| 56 ft | 2.76 | 1.84 | 0.76 | 1.14 |
| 58 ft | 2.58 | 1.71 | 0.68 | 1.02 |
| 60 ft | 2.41 | 1.60 | 0.62 | 0.92 |
- Factored and allowable loads are limited by bending, or by shear where marked *.
- The deflection columns are the service loads that make the beam sag span/360 or span/240. Compare span/360 with the live load alone and span/240 with dead plus live load, the usual floor limits in IBC Table 1604.3.
Reading the table
At a 36 ft span, a W24×104 carries a factored load of 6.69 kips per foot (LRFD) or an allowable load of 4.45 kips per foot (ASD). A live load of 2.85 kips per foot would deflect it span/360, which is 1.20 in. The beam works if the factored load is under the first number and the live and total loads are under the deflection numbers. For other spans, supports or loads, open it in the beam designer, or follow the steel beam design guide to check one by hand.
W24×104 questions
What does W24×104 mean?
W means a wide flange shape. 24 is its nominal depth in inches (the actual depth is 24.1 in) and 104 is its weight in pounds per foot.
How much does a W24×104 weigh?
104 pounds per foot, so a 20 ft W24×104 weighs about 2,080 pounds.
How far can a W24×104 span?
It depends on the load. Braced along its length, it carries 60.2 kips per foot of factored load at 12 ft and 2.41 kips per foot at 60 ft; the load table has the spans in between. Floor beams are often 36 to 48 ft for this depth (span-to-depth ratios of about 18 to 24), where deflection usually governs.
Is a W24×104 a compact section?
Yes. Its flanges (bf/2tf = 8.50) and web (h/tw = 43.1) are both compact for bending in 50 ksi steel.